In recent years, endoscopic surgery has become the accepted standard for conducting many types of surgical procedures, both in the medical and dental arenas. The availability of imaging devices enabling a surgeon or dentist to view a particular surgical area through a small diameter endoscope which is introduced into small cavities or openings in the body results in much less patient trauma as well as many other advantages.
In many hospitals, the rod lens endoscope is still used in endoscopic surgery. The rod lens endoscope includes a very precise group of lenses in an elongate and rigid tube which are able to accurately transmit an image to a remote camera in line with the lens group. The rod lens endoscope, because of its cost of manufacture, failure rate, and requirement to be housed within a rigid and straight housing, is being increasingly replaced by solid state imaging technology which enables the image sensor to be placed at the distal tip of the investigating device. The three most common solid state image sensors include charged coupled devices (CCD), charge injection devices (CID) and photo diode arrays (PDA). In the mid-1980s, complementary metal oxide semiconductors (CMOS) were developed for industrial use. CMOS imaging devices offer improved functionality and simplified system interfacing. Furthermore, many CMOS imagers can be manufactured at a fraction of the cost of other solid state imaging technologies.
One particular advance in CMOS technology has been in the active pixel-type CMOS imagers which consist of randomly accessible pixels with an amplifier at each pixel site. One advantage of active pixel-type imagers is that the amplifier placement results in lower noise levels than CCDs or other solid state imagers. Another major advantage is that these CMOS imagers can be mass produced on standard semiconductor production lines. One particularly notable advance in the area of CMOS imagers including active pixel-type arrays is the CMOS imager described in U.S. Pat. No. 5,471,515 to Fossum et al. This CMOS imager can incorporate a number of other different electronic controls that are usually found on multiple circuit boards of much larger size. For example, timing circuits, and special functions such as zoom and anti-jitter controls can be placed on the same circuit board containing the CMOS pixel array without significantly increasing the overall size of the host circuit board. Furthermore, this particular CMOS imager requires 100 times less power than a CCD-type imager. In short, the CMOS imager disclosed in Fossum et al. has enabled the development of a "camera on a chip."
In addition to active pixel-type CMOS imagers, passive pixel-type CMOS imagers have very recently been improved so that they too can be used in an imaging device which qualifies as a "camera on a chip." In short, a passive pixel-type imager does not perform signal amplification at each pixel site.
Although the camera on a chip concept is one which has great merit for application in many industrial areas, a need still exists for a reduced area imaging device which can be used in even the smallest type of endoscopic instruments in order to view areas in the body that are particularly difficult to access, and to further minimize patient trauma by an even smaller diameter invasive instrument.
It is one object of this invention to provide surgical instruments with reduced area imaging devices which take advantage of the CMOS-type imagers of Fossum et al., or passive pixel-type CMOS imagers, but rearrange the accompanying circuitry in a stacked relationship so that there is a minimum profile presented when used within the surgical instrument. It is another object of this invention to provide low cost imaging devices which may be "disposable." It is yet another object of this invention to provide a reduced area imaging device which may be used in conjunction with standard endoscopes by placing the imaging device through channels which normally receive other surgical devices, or receive liquids or gases for flushing a surgical area. It is yet another object of this invention to provide a surgical device with inherent imaging capability which may be battery powered and only requires one conductor for transmitting a pre-video signal to video processing circuitry within or outside the sterile field of the surgical area.
In addition to the intended use of the foregoing invention with respect to surgical procedures conducted by medical doctors, it is also contemplated that the invention described herein has great utility with respect to oral surgery and general dental procedures wherein a very small imaging device can be used to provide an image of particularly difficult to access locations. Additionally, while the foregoing invention has application with respect to the medical and dental fields, it will also be appreciated by those skilled in the art that the small size of the imaging device set forth herein can be applied to other functional disciplines wherein the imaging device can be used to view difficult to access locations for industrial equipment and the like. Therefore, the imaging device of this invention could be used to replace many industrial boroscopes.
The CMOS image sensor technology can be furthered improved with respect to reducing the profile area of the "camera on a chip" and incorporating such a reduced area imaging device into very small investigative instruments which can be used in the medical, dental, or industrial fields.